1. Field of the Invention
This application pertains to precast concrete structures of various sizes and shapes which are suitable for installation as integrated systems to form seawalls and various shoreline reinforcement systems for limiting shoreline erosion by rivers, lakes, oceans, sounds and other major bodies of water, as well as terrestrial structures for terracing, dams, bridges, buildings, etc.
2. The patent referred to above provides a summary of relevant prior art. While many techniques have been developed for reinforcing shorelines, as described in that patent and various publications of the U.S. Army Corps of Engineers, there is still considerable room for improvement. Applicant""s company Seament Shoreline Systems, Inc. of Virginia and its subcontractors have completed several shoreline installations using the components and methods disclosed in the above patent. The Corps of Engineers publication xe2x80x9cLOW COST SHORE PROTECTION . . . a Property Owner""s Guidexe2x80x9d discloses at page 154 the use of precast open concrete boxes filled with sand to form waterfront sills to retain perched beaches. U.S. Pat. No. 5,697,736 discloses in columns 8-9 the use of precast concrete boxes as alternatives to Double xe2x80x9cTxe2x80x9d units (discussed below) for constructing pier-groins extending seaward from a seawall and for use in forming underwater and near-shore) breakwaters. Columns 12-13 and FIGS. 20 to 25 discuss the use of such concrete boxes to form floating pier assemblies.
Catalogs of Admiral Marine Co. (Staten Island, N.Y., New Orleans, Oakland, Calif. and Chicago) and Peck and Hale (West Sayville, N.Y. and Kowloon, HONG KONG) disclose various metal fastening devices which could be employed to connect certain components of the present invention to form structures.
Changing weather patterns and rising sea levels have increased the risk of shoreline damage from hurricanes and other storms, while environmental and zoning laws in many cases make it very difficult to rebuild shoreline structures which are destroyed or damaged. Accordingly, it is prudent for both private owners and governmental bodies to take timely steps to protect waterfront installations from foreseeable damage. Normally, large stone rip-rap revetments, groins or breakwaters have been used for such protection. However, these methods require that a large total mass of materials be transported to the site. Such rocks are difficult to handle, cannot be interconnected or floated into place and are not easily relocatable. Furthermore, such rocks are not amenable to intermodal transport or use in a modular system.
An object of the present invention is to provide easily transportable construction components which can be used to control shoreline erosion. As another object, such components should be provided in sizes, shapes and proportions which are compatible with existing trucks, railcars and maritime transportation modes as well as adapted to existing materials handling equipment. As a further object, the components should be transportable in segments so that they can be moved into positions for installation through crowded beachfront areas, by land, water or aircraft such as heavy lift helicopters, blimps or dirigibles.
Another object of the invention is to provide such construction components as partially-closed containers which are light in weight but can be filled with available liquid or solid materials at the installation site to substantially increase their mass at little cost. A further object of the invention is to provide construction components which can be filled with solids, gases or liquids to increase their masses when installed as part of a structure, simultaneously serving as sealed storage containers for such materials for later use.
An additional object of the invention is to provide construction components which have the largest masses practicable when filled with ballasting material and installed to form structures. Maximizing the mass of such components is desirable to equip the structures to resist the large forces generated by storm waves, currents, floods, mudslides, earthquakes and other natural disasters. Such maximizing of mass can have similar applications in combat engineering, where enemy artillery, bombardment and demolitions may be encountered. The underlying physical principle is expressed by the equation F=ma, i.e. force equals mass times acceleration. The forces generated by mudslides, floods, hurricanes and large storm waves, currents, etc. can be very strong. (See calculations in columns 17-20 of the patent referred to above.) However, if the resisting mass of an object is very large (especially in comparison to the surface area against which water pressure is exerted), the resulting acceleration of the object in response to a large force can be relatively small.
Thus, it is an object of the invention to provide construction components which have ratios of surface areas and installed masses to successfully resist the forces which can be reasonably foreseen for the installation area. A further object is to provide such components which can be connected together when installed to form a structure, thus providing very massive structures which will successfully resist the worst forces of nature with very little acceleration response or damage.
Still another object of the invention is to provide intermodal sets of precast concrete boxes which can be used as construction components for various civil, marine, commercial or military construction projects. Such components could be connected together to form causeways, fixed or floating bridges, dams, drilling rigs, floating or fixed airport runways or helicopter pads, temporary or permanent shipping ports, temporary military or naval facilities, xe2x80x9ccontainer shipsxe2x80x9d, relocatable modular waterfront structures such as houses, and many other applications.
Another object of the invention is to employ recyled materials in the concrete mix where possible to reduce material costs as well as to help protect the environment. For example, fly ash from power plants can be successfully used in various concrete mixtures for casting the construction components. Used tires can be used as gasket or cushioning material to be placed between the precast constructions components in some installations.
Still another object of the invention is to provide methods of installing precast concrete boxes in underwater positions by transporting them on floating vessels and/or floating them into approximate position and sinking them into their final installed positions. A related object is to provide vessels which are suitable for transporting such boxes, either as deck cargo or as a floating component of the vessel itself.
Yet another object of the invention is to provide shellfish habitats based upon precast concrete boxes which will allow shellfish to grow in underwater areas separated from pollution or silting and facilitate convenient and effective harvesting of the mature shellfish.
In accordance with the present invention, improved versions of the L-members of the previous patent (having vertical walls, horizontal footers, vertical keys protruding below the footers and an angular splash plate protruding from the member directly opposite the footer), with at least one substantially vertical passage penetrating the splash plate and key, with an upper inlet and a lower outlet to facilitate setting the L-members in place by use of fluids comprising water under pressure emerging from the lower inlets of the passages. These L-members can be further improved by adding accessories including:
a) precast concrete components comprising channels adapted to form a cap atop the vertical wall portion of an L-member and mechanically attached thereto, and sections extending horizontally from the channels when the cap is in place, forming horizontal support surfaces substantially perpendicular to the vertical wall portion;
b) precast concrete components which are fastened to the upper surfaces of the horizontal sections described above, approximately perpendicular thereto, and either affixed thereto by mechanical attachments or precast as a unit therewith;
c) longitudinal precast concrete components having channels in each end, with one channel adapted to fit the top of the vertical wall portion of the L-member and emplaced thereon, with the other channel being adapted to accommodate a horizontal railing member which is placed atop the longitudinal members and fitted in the channels thereof to form a railing atop the vertical wall portion of the L-member;
d) precast concrete channel components having the cross-section of a squared letter xe2x80x9cUxe2x80x9d, with the groove adapted to fit the top of the vertical wall portion of the L-members, these channel components being emplaced atop the L-members to form a cap atop the vertical wall portion thereof;
e) precast concrete components forming a step cap, comprising a portion to be attached to the upper portion of the vertical wall portion of an L-member, a portion extending downward therefrom at an obtuse angle to the vertical, and forming at least two stair steps extending from the top of the vertical wall portion to the base of the L-member, normally comprising bracing means extending between the underside of the stair steps and the splash plate and/or vertical wall portion of the L-member to provide support for the stair steps.
As disclosed in the previous patent, these improved L-members can be assembled to form structures such as sea walls or bulkheads, and used in conjunction with precast concrete components placed perpendicular to such a sea wall as groins to form shoreline reinforcement systems. A variety of precast concrete components can be used to form such systems, including T-walls, pi-walls, precast concrete boxes and the like, and concrete mat sections can be used to fill in horizontal spaces between such groins.
Precast concrete boxes of various types, including those disclosed in the previous patent and new versions described below, can be used to form many structures, including sea walls or bulkheads and shoreline reinforcement systems based thereon, which may include such precast boxes and/or other precast components discussed above to form groins, horizontal sections, breakwaters and the like. Precast concrete boxes can also be employed to construct waterfront boathouses, either with solid foundations or floating bases, and modular structures suitable for dwellings, offices or shops.
Novel systems of precast concrete boxes are provided which generally have the overall form of rectangular parallelepipeds. The boxes can be enclosed on all sides and provided with means for flooding with water and subsequently expelling the water using air pressure or pumping means to raise the sunken boxes. Alternatively, they can include openings such as holes or slots, as disclosed in the previous patent. These and even the precast concrete boxes previously disclosed can be produced in sets, including at least two different sizes and sets of proportions which permit the boxes to be conveniently shipped together by intermodal means of transport and also assembled together to form various structures. The boxes have at least one dimension adapted to fit conveniently into at least one transportation mode such as truck trailers, rail cars and container ships, with a set including a plurality of boxes having at least two different combinations of dimensions and/or proportions. The smaller boxes have at least one dimension which is a whole number fraction of the corresponding dimension of the largest box of the set, which might be termed the xe2x80x9cmaster boxxe2x80x9d. The boxes can be divided by horizontal or vertical partitions into at least two separate inner compartments which can be independently flooded or blown, with valves adapted to equalize air pressure and/or liquid contents between these compartments. In some embodiments, these boxes can have removable concrete tops.
An embodiment of the enclosed boxes described above which is suitable for constructing bridges and the like has the overall form of a rectangular parallelepiped with five surfaces substantially enclosed, the sixth surface having the largest dimension of the box and the two surfaces adjacent thereto being cut out to form a channel adjacent to the sixth surface when it rests upon the ground. The portion of the box below such cutouts can be left open or joined with an enclosure to seal the box on all sides. Inlets can be provided to fill such boxes with sand, water or the like.
Various types of precast concrete boxes of the invention (and even the prior art) can be assembled to form waterfront structures such as boathouses, either on solid foundations or on floating assemblies of the boxes. With solid foundations, the cutout boxes described above can be emplaced upon the bottom to allow for the flow of water currents.
The enclosed precast concrete boxes of the invention can be interconnected together by mechanical means to form bundles or assemblies like log booms to be towed or otherwise transported over water. Further in accordance with the invention, such interconnected groups of concrete boxes which form a large rectangular mass can be transported by a self-propelled vessel for transporting floating objects which comprises separate bow and stern sections adapted to be fastened together using mechanical means to form the vessel alone. When used for transporting such assemblies of boxes (or other interconnected groups of floating objects such as logs, containers, tanks, floating drydocks or the like), the two sections of the vessel are separated and connected to the ends of the group of boxes to form a xe2x80x9cstretchedxe2x80x9d vessel in which the group of boxes forms a midship section. The vessel is provided with conventional propulsion systems (in the stern section), thruster propulsion units to aid in maneuvering, anchors and power supplies for their operation and at least one crane for unloading and emplacing the boxes or other cargo at destination.
Further in accordance with the invention, certain embodiments of the precast concrete boxes are used to form shellfish habitats, and are preferably cast from concrete comprising crushed bivalve shells. Oyster shells are preferred, but any calcareous shells can be used, such as clam, mussel or conch shells. The boxes can have holes and/or slots in the walls, which can be temporarily plugged with knockout sections to facilitate sinking the boxes in the water, and removable concrete tops. The tops can include various projections on one side (which is emplaced inside the box during transport, then reversed to face outward and upward during installation) to provide optimum surfaces for young shellfish to adhere to. The projections can have the form of cylinders, conical sections or rectangular parallelepipeds, cast integrally with the tops or mechanically affixed thereto. The tops can also be cast with broken bivalve shells (such as oyster shells) adhering to the outer surface, to provide natural shell surfaces for the young shellfish to adhere to. Means are provided for removing and hoisting the lids of such shellfish habitats for harvesting, and/or for expelling the water within enclosed versions of the boxes and floating and/or hoisting them to the surface.
In another embodiment, a shellfish habitat comprises a rectangular meshwork container comprising a rigid frame and meshwork enclosure surfaces to retain therein various objects which may provide appropriate shellfish habitat. The container has a shape and size suitable for emplacement atop precast concrete boxes as discussed above, and to accept precast concrete tops fitted with projections for shellfish culture, also as described above. The container and/or cover are fitted with cables or other mechanical devices for hoisting out of the water for harvesting of shellfish.
The precast concrete boxes of the invention can be installed in the water along a shoreline by sealing all inlets below the expected waterline of the installed boxes, placing the boxes in the water and floating them into position, then opening sufficient water inlets and air outlets to allow the boxes to sink into their assigned places. In preferred embodiments, these inlets and outlets can be opened remotely, and guidance can be provided to the boxes while they are being sunk into position. A group of such boxes can be interconnected and emplaced beneath the water to form a submerged breakwater or reef by positioning the connected boxes atop a flat deck of a vessel, emplacing an anchor on the bottom near the planned installation position and attaching same to a cable slidably connecting the boxes on deck, launching the boxes into the water while the vessel proceeds forward away from the anchor, then maneuvering the boxes into end-to-end contact and clamping the resulting string of boxes into place on the cable, placing the resulting floating string of boxes into position directly above the planned installation position, and finally, sinking the boxes while guiding them into final position by securing the forward end of the cable to a second anchor at the opposite end of the string from the first anchor and applying tension to the cable from the vessel.
The vessel used can be a barge, a vessel with a bow door and ramp (such as Navy landing ship tank, landing craft mechanized, landing craft vehicle and personnel and the like) or a vessel with an after well deck affording access to the water for floating boxes directly into the water (such as a Navy landing ship dock). A container ship with a flat deck and cranes to hoist the boxes from deck level to water level can also be used.
Additional objects and advantages of the present invention are described in, and will be apparent from, the following detailed description of preferred embodiments together with the drawings and appended claims.